2. The curve \(C\) has equation
$$x ^ { 2 } - 3 x y - 4 y ^ { 2 } + 64 = 0$$
- Find \(\frac { \mathrm { d } y } { \mathrm {~d} x }\) in terms of \(x\) and \(y\).
- Find the coordinates of the points on \(C\) where \(\frac { \mathrm { d } y } { \mathrm {~d} x } = 0\)
(Solutions based entirely on graphical or numerical methods are not acceptable.)